Fuel pump issue / fuel boiling

[Russtee]

Hey everyone,

Has anyone had any issues with there fuel pump bubbling/producing bubbles when running or boiling fuel at all?

I have a 2016 350 rr. Pretty sure whoever put this bike together at the factory was hungover or it was the last one to be assembled and they used all the crappy left over parts lying around.

It happened once before a couple of years ago, turned the fuel tank into a balloon before i noticed it as I was racing down some single track.
Figured it was some bad fuel and it didnt happen again until first ride this spring.

Any infomation is appreciated.

Cheers

[BDM]

Engine/cooling system gets hot then some heat is transferred to the tank and gas. Gas can begin to vaporize @ about 93 deg F and boil @ about 181 deg F depending on blend and altitude.
So with normal operating temps of 190-230 deg F it is no surprise there is some gassing of fuel. Some add heat insulating material to the underside of the fuel tank to help.
Sounds to me like you have a fuel tank venting issue. Remove the check ball from cap and don't use one of those aftermarket one way valves on the tank breather.

Bruce

[hawaiidirtrider]

BDM got it pretty much. Venting issues happen with a bunch of different bike brands. . Betas have had issues with that ball valve at times. Just take it out and clear and that usually fixes it. I’ve had issues with my 525 RS Beta years ago and my honda. Once the vent in the cap is cleared Ive had no issues. I bought insulation to go on the underside of my gas tank but never put it on once my vent in my cap was addressed.

[Russtee]

Hey guys thanks for your replies.
Although the ball valve is not the issue.

The pump is creating bubbles.
When the bike is running there is a steady flow of small bubbles coming from the pump.
As it gets hotter the bubbles get larger and even with the bike off the fuel is boiling around the pump.
This is what is pressurising the tank.
I now run it without the ball valve until i can get a new pump.
Not ideal.

[aj_mariner]

Is there a fuel pump inlet strainer? Have you tried cleaning it?

[hawaiidirtrider]

Hey guys thanks for your replies.
Although the ball valve is not the issue.

The pump is creating bubbles.
When the bike is running there is a steady flow of small bubbles coming from the pump.
As it gets hotter the bubbles get larger and even with the bike off the fuel is boiling around the pump.
This is what is pressurising the tank.
I now run it without the ball valve until i can get a new pump.
Not ideal.

Keep an open mind that may not be the singular issue.. A variety of bikes not with a fuel pump have the gas boil and tank expand. My 525 RS Beta did and my Honda cr 250 too. Both carbed bikes.. the fuel was still boiling after shutting off etc. I changed gas caps to have very free flowing venting and put cooling mods like a fan and increased coolant volume etc. You are the first Ive heard of a fuel pump creating boiling gas. I have bought insulation to put on the underside of the gas tank to insulate heat but after doing other mods the boiling didn’t happen anymore. Try to google boiling gas and see what other options others have done to address this as there be more ideas not mentioned here.